In a plasma processing apparatus having an ICP (inductive coupling plasma) antenna installed outside a chamber, since a high frequency power from the ICP antenna connected to a high frequency power supply cannot be transmitted through a conductor, a ceiling portion of the chamber which is opposite to the ICP antenna is formed as a dielectric window made of, e.g., quartz; and the high frequency power applied to the ICP antenna is supplied into the chamber through the dielectric window. The high frequency power supplied into the chamber excites a processing gas, so that a plasma is generated.
The dielectric window needs to have a thickness that ensures enough stiffness to endure pressure differences between a depressurized environment inside the chamber and an atmospheric pressure environment outside the chamber. Further, along with the trend toward scaling up of a semiconductor wafer, the dielectric window opposite to the semiconductor wafer also needs to be scaled up. Further, the dielectric window needs to have enough stiffness to manage the scaling up of the semiconductor wafer, and thus requires a thicker thickness.
However, as the dielectric window becomes thicker, the high frequency power transmitted therethrough is decreased, which results in a decrease of plasma generation efficiency. Moreover, due to the high-cost of quartz forming the dielectric window, the cost of the plasma processing apparatus rises as the dielectric window becomes thicker.
Accordingly, there has been proposed a plasma processing apparatus 114 in which a ceiling portion 111 of a chamber 115 which is opposite to an ICP antenna 110 is made of a relatively inexpensive conductor having high stiffness, e.g., a plate-shaped member made of aluminum; a plurality of slits 112 are provided to extend through the ceiling portion 111 and respectively covered by dielectric windows 113; and a part of the ICP antenna 110 is made to face the inside of the chamber 115 through the dielectric windows 113, as shown in FIG. 11 (see, e.g., Patent Document 1).
In the plasma processing apparatus 114, the size of each of the dielectric windows 113 can be reduced since the respective dielectric windows 113 are provided to cover the slits 112 only. Accordingly, it is unnecessary to increase the thickness of the dielectric window 113 in order to ensure stiffness.
Further, there has been proposed a plasma processing apparatus using both parallel plate electrodes and an ICP antenna (see, e.g., Patent Document 2). Specifically, as shown in FIG. 12, a plasma processing apparatus 120 includes parallel plate electrodes having a mounting table 121 serving as a lower electrode and a shower head 122 serving as an upper electrode; and a dielectric window 123 that is a ring-shaped dielectric member arranged so as to surround the shower head 122. At the central portion of the chamber 124, a plasma of a processing gas is generated by a high frequency power applied from the parallel plate electrodes. At a peripheral portion of the chamber 124, the plasma of the processing gas is generated by a high frequency power applied from the ICP antenna 125 through the dielectric window 123. Accordingly, with this plasma processing apparatus 120, the size of the dielectric window 123 can be reduced since the ceiling portion of the chamber 124 does not need to be entirely formed with the dielectric window 123. As a result, it is unnecessary to increase the thickness of the dielectric window 123 in order to ensure stiffness.
Patent Document 1: Japanese Patent No. 4193255
Patent Document 2: Japanese Patent No. 3192352
In the plasma processing apparatus 114 described in Patent Document 1, however, the high frequency power passes through the slits 112 only, so that the plasma density at the regions that correspond to the slits 112 in the chamber 115 is only increased. This leads to a non-uniform distribution of the plasma density. Further, the positions and the sizes of the slits 112 cannot be changed since the slits 112 are formed by making holes in the thickness direction in a plurality of portions of the ceiling portion 111. Therefore, the control of the plasma density distribution in the chamber 115 is limited.
Further, in the plasma processing apparatus 120 described in Patent Document 2, the position and the size of the perimeter of the annular coils of the ICP antenna 125 cannot be changed. Hence, the control of the plasma density districution in the chamber 124 is limited.